It quit again, it was running about 5 or 6 hours before the CP rebooted.
This seems longer than when it was on a subbed acct, but that is anecdotal.

The next goaround, about 2 or 3 hours, it quit out to the unsubscribed clock.  So it seems this is probably no different from being subscribed, as Duane suggested.  Except perhaps the "network timeout"  I haven't seen that before.

I have the unsubscribed test unit still quitting while playing pandora.  My sense is it plays some amount longer than it did when it was subscribed, but that is anecdotal.  I can't say for sure.

Today, I started Pandora on the unsubscribed I3, and it quit out immediately to the unsubscribed widget. 
It didn't play at all. 

I clicked pandora again and it played normally, quit a number of hours later.

On my old chumby which has power connector issues I was having issues with it occasionally dropping off the network, that may be what's happening here.

Now this is new.

My I3.5 on my desk was playing Pandora, and then it quit, like it's been doing. It does that several times a day.
Rebooting, seemingly.

But I notice that the thing has been playing widgets for several minutes, and the song that Pandora was playing is still playing.
I haven't noticed that before.
It seemed to all quit together.

I thought I'd mention this in case it's a clue to the problem.

Or it may be that the way Pandora works is the song is downloaded and plays and then the next is downloaded and plays.
Not really streaming, which makes a lot of sense.

But today it seems the part of Pandora that plays the song didn't crash with the rest of it.

I have been listening to Iheart Radio on an I3.
I notice that it sometimes crashes too.
In fact it crashes quite often. I am thinking it might be twice or three times as much as Pandora.
It crashed and rebooted about 30 minutes ago, and the I3 is now playing a channel, but the Iheart stream still plays.
I've seen this a few times. Pandora would crash and the unit would reboot but it stops playing.
I heart at least sometimes keeps playing.
So it seems the problem might not be just Pandora, it might be all the audio players.
I do notice that if I leave Iheart paused, set for a station but not playing, it can sit like that for days or weeks.
This only happens when the audio is playing. Or so it seems.

I wonder if the function that actually plays the audio is a function or package that maybe there's an upgrade for?

Something has changed in the last few months.
I first noticed this when streaming Iheart.
The channel will be playing, and then the UI quits, and the unit reboots.
During all this the music will continue to play. When it reboots it starts playing widgets but the music continues.
I can reselect the Iheart channel I was listening to and click controls and can pause, etc.
Or quit the music from playing.
It seems that now, the UI is what quits, not the streaming. A year ago they would both quit.
It happens pretty fast, maybe within a half an hour with Iheart.

I think Pandora does the same.  I will check it.
I do notice that if I pause the sound on either source that crash does not occur.
The screen can sit there for days without issue. As long as the sound is not playing.

I did notice that when streaming iHeart, and the UI quits, and this now happens pretty immediately, the sound continues to play after the UI has quit.
I go back to the music list, and normally at the top it lists what is currently playing.
But not for iheart. Not after the UI quits.
If I restart the iHeart UI I can go back to the channel I was listening to and can pause it, for instance. So something is still connected.
If I exit the iHeart UI the music menu does list the source that is currently playing.
I am leaving it on that screen for a while to see if the music menu ever quits.
OK, the menu did quit. Initializing. iHeart is still playing. Widgets resumed playing.
I go back to the music menu and the source that is still playing is not listed at the top.
I go back to iHeart and I am able to then pause the source that is playing.
The music menu now lists the iHeart source again.

Hmmm, I'll see if I can reproduce this - I have a device in my office that I play both iHeart and Pandora, but I'm not seeing this behavior.

Just to eliminate widgets as a possible cause, can you run a very simple channel with a couple of clocks to see if it has any effect?

This is interesting. As you asked I created a channel with a couple of clocks. Space clock and one of the flip clocks.
Switched to it.
It was playing.
Clicked the button, picked music.
Picked iheart.
Picked a channel.
It plays. Space Clock.
Immediately stops, the music stays streaming,
One of the widgets from the channel I was playing appeared briefly, then it said initializing, checking network.
Sound is still playing.
Space clock is displayed.  Crazy.

I did notice something new on Iheart. There is a message there most of the time saying "Spot Block End."
That might have something to do with it. I think that is new.
And at the moment I do not see any ads on the right. There have been times when I have but not right now.